Find the tire code on the sidewall, such as P215/65R15 95H
P = tire type
P = passenger vehicle tire
LT = light truck tire
ST = special trailer tire
T = temporary spare tire
215 = section width in millimeters
65 = aspect ratio, or sidewall height as a percentage of width
R = radial construction
D = diagonal or bias-ply construction
B = belted bias construction
15 = wheel diameter in inches
95 = load index
H = speed rating
Load index = maximum load capacity
Speed rating = maximum safe speed
Metric tire sizes use width/aspect ratio/construction/wheel diameter format
Flotation sizes use overall diameter x width x wheel diameter format
Example: 31×10.50R15
31 = overall tire diameter in inches
50 = tire width in inches
R = radial construction
15 = wheel diameter in inches
Compare tire size to vehicle manufacturer specifications
Match load index and speed rating to vehicle requirements
Ensure tire size fits the wheel and vehicle clearance
Check the owner’s manual or driver-side door placard for recommended size